That's what makes Tennis different and special. Other sports don't have the kids officiate their own match either.

It's one of the things, but not the only thing. Its also one of the things that turn what could eventually be exceptional players away from the game at an early age. some kids are just not ready to deal with isolation at a very young age. For under 12's, coaching can sometimes be as simple as a hug and some reassuring words. Yes, they have to transition to real rules sometime, like they have to transition from green to yellow balls.
And there are other sports where kids officiate there own matches, such as golf.